Carrying device for electroplating and method for improving the delivery of current therein

ABSTRACT

A carrying device for electroplating and method for improving the delivery of current therein. The carrying device comprises a core of a high conductivity material and a cladding shrunk around and sealing the core, the cladding having a second, moderate conductivity material which, however, has a high resistance to acidic corrosion. The device further comprises a plurality of electrically conductive clamping members of the second material for clamping an article to be electroplated and for delivering current thereto. Current flow to the clamping members is improved by respective pins consisting essentially of the second material, the pins being forced into respective undersized apertures provided near the clamping members.

TECHNICAL AREA

This invention relates to a carrying device for delivering a largeelectrical current to an article to be electroplated while immersed in aplating solution, the device also being adapted for immersing the samearticle in an acidic etching solution for etching the article. Moreparticularly, this invention relates to such a carrying device adaptedfor etching and electroplating panels of printed circuit boards and tomethods for improving the delivery of current in such a carrying device.

BACKGROUND OF THE INVENTION

It is often necessary to deposit a metal layer onto a base metal, forexample, to alter the appearance of the base metal, or to provide thebase metal with improved hardness, corrosion resistance or conductivity.One common process for depositing such a layer is by electroplating. Itis also often necessary to remove metal from an article. A commonprocess for this latter purpose is to etch the article in an acidicsolution. In the manufacture of some articles, such as printed circuitboards, both etching, to define a circuit pattern on a copper cladfiberglass substrate, and electroplating, to improve the solderabilityand contact conductivity of the circuit pattern, are often employed.Both of these processes are advantageously carried out by immersing thearticle in a solution. When electroplating, an electrical current mustbe delivered to the article while it is bathed in a plating solution,and when etching the article is bathed in an acidic etching solution. Itis highly desirable that the article be carried through both processesby the same means without having to be removed from one device andtransferred to another. Moreover, other processing steps are oftendesired to be accomplished while the article is being carried,particularly, a drying step accomplished at an elevated temperature isoften advantageous. Accordingly, it has been a goal in the art toprovide a carrying device adapted to (1) clamp securely an article, (2)provide for the delivery of an electrical current to the article, and(3) provide resistance to: (a) the build-up of metal on the carryingdevice, (b) the acids employed in the etching process, and (c)temperature cycling.

In the electroplating of panels of printed circuit boards, a number ofspecific difficulties arise that further challenge the design of suchcarrying devices. First, relatively large electrical currents musttypically be used, in accord with the relatively large surface area of apanel and the relatively low voltages employed. Moreover, it isimportant to deliver this large current uniformly across the article, tocontrol plating thickness, to ensure adequate coverage and at the sametime to spare often precious plating metals.

Common prior art carrying devices employ a soft conductor, such ascopper, a number of clamping members silver soldered to the softconductor, and a conformal plastic coating having apertures inside theclamping members allowing metal to contact the article at selectedlocations within the clamping members for current carrying to thearticle. Since the conductor is soft, it is often not strong enough tomechanically support the article, particularly when it is in an elongateform as is common. Thence, strengthening of the conductor is oftenaccomplished by attaching a bar or rod of stainless steel thereto withbolts. There are a number of problems with these devices have beennoted. First, during temperature cycling, the dissimilar materialsexpand and contract at different rates and, thence, loosen theattachment bolts. This reduces the strength of the carrying device and,further, alters current carrying capacity and therefore overallconductivity.

Moreover, looseness between the parts within the conformal coatingallows cracks to develop therein, which breaches its integrity. Cracksor pin-holes in the coating resulting from any number of sources, suchas manufacturing defects, or as a result of aging, temperature cyclingand mechanical damage during use, allow fluid to contact the conductor.Common etchants, such as nitric and sulfuric acid, attack the copper anddestroy its integrity. These solutions also attack the silver solderjoint supporting the clamping members, through which large currents mustbe conducted and by which an even distribution of current through thesurface of the article is expected. Once the etchant begins to attackthe material underneath the coating, the coating becomes lifted,permitting an accelerated attack. Destruction of the carrying device canbe dismayingly rapid once the coating is breached.

Another means of protecting a conductor in a corrosive environment isproposed in Lang, U.S. Pat. No. 5,094,735, disclosing a central coppercore which is covered by a protective layer of 316 stainless steel ortitanium for corrosion resistance. The layer is said to be welded to thecore; however, the welding can only occur at localized portions thereof,limiting electrical conductivity and introducing imbalances in currentdistribution throughout the device.

Still another means of protecting a conductor in a corrosive environmentis proposed in Mallock, U.S. Pat. No. 4,540,478. "O"-rings are utilizedfor sealing a bus-bar within a tubular member to prevent fluid contactwith the buss-bar. However, "O"-rings are prone to leakage anddeterioration, particularly if they are not compressed properly or areused in hostile environments.

Other means of electrically joining an article to a carrying device forthe delivery of a controlled amount of current to the article employ ascrew connection in the attachment of a clamping member to a conductorbar for the delivery of current from the conductor bar to an article.See e.g., Mallock, supra., Belke, U.S. Pat. No. 3,001,926, and Lang Jr.,U.S. Pat. No. 5,094,735. However, a screw attachment of a stud to aconductor bar depends sensitively for its current carrying capacity onthe compressive stress at the threads, which, in turn, depends on propertorquing of the screws. Further, during temperature cycling, screws areprone to loosen so that the compressive stress and, therefore, theconductivity of the joint, will undesirably change with use.

SUMMARY OF THE INVENTION

In accordance with this invention, an improved carrying device forelectroplating and method for improving the delivery of current thereinis provided. The improved carrying device comprises a core consistingessentially of a first, relatively high conductivity material and acladding shrunk around and sealing the core, the cladding consistingessentially of a second material having only moderate conductivity buthaving a high resistance to acidic corrosion. The carrying devicefurther comprises a plurality of electrically conductive clampingmembers, consisting essentially of the second material, joined to thecladding, and an acid resistant, pliable, conformal coating over thecladding and the clamping members. However, clamp apertures are providedthrough the coating for exposing a high conductivity contact surface ofeach clamping member. Each of the clamping members include a tighteningmember for gripping, between the tightening member and the contactsurface of the clamping member, an article to be electroplated or aportion of the article, so that electrical contact is made between thearticle and the clamping members. Current flow from the core to theclamping members is improved by employing respective pins consistingessentially of the second material, the pins being forced intorespective undersized apertures provided near the clamping members, theapertures being formed through the cladding and either partially orcompletely through the core.

Therefore, it is a principal object of the present invention to providea novel and improved carrying device for electroplating and method forimproving delivery of current therein.

It is another object of the present invention to provide such a carryingdevice and method for improving delivery of current therein whichprovides a long service life.

It is yet another object of the present invention to provide such acarrying device and method for improving delivery of current thereinwhich provides for a well controlled distribution of current to anarticle to be electroplated.

It is still another object of the present invention to provide such acarrying device and method for improving delivery of current thereinwhich provides for current carrying connections which do not degradesignificantly during the service life.

The foregoing and other objects, features and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation of an improved carrying device for electroplatingaccording to the present invention.

FIG. 2 is a pictorial view of a bus connector of an improved carryingdevice for electroplating according to the present invention.

FIG. 3A is a pictorial view of a cladding of an improved carrying devicefor electroplating according to the present invention.

FIG. 3B is a cross-section along line A--A in FIG. 3A.

FIG. 4 is a pictorial view of an anchor of an improved carrying devicefor electroplating according to the present invention.

FIG. 5A is a first pictorial view of a pin aspect of the device of FIG.4.

FIG. 5B is a section along line B--B in FIG. 5A.

FIG. 5C is a second pictorial view of the pin of FIG. 5A.

FIG. 6 is a pictorial view of a conformal coating of an improvedcarrying device for electroplating according to the present invention.

FIG. 7A is a pictorial view of a spaced-apart groove of an improvedcarrying device for electroplating according to the present invention,with cladding cut-away.

FIG. 7B is a side view of the spaced-apart groove of FIG. 7A, withcladding cut-away.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a preferred embodiment of an improved carryingdevice 10 for electroplating and method for improving current deliverytherein according to the present invention employs a conductor, such asan elongate conductor bar 12, in conjunction with an existing buss, suchas a buss bar 11, providing a cathodic current and to which theconductor bar mechanically and electrically attaches, and an existingsolution bath 13, in which the conductor bar 12 is partially immersed.An article 15 to be plated is attached, mechanically and electrically,to the conductor bar 12, and this attachment may be advantageouslymaintained when the article is to be etched. In the electroplating of aprinted circuit board panel, the conductor bar 12 is typically requiredto carry and deliver to the panel about 75 Amps at 2 volts and,therefore, a relatively small voltage drop--on the order of tenths of avolt or less--is tolerated. A "good" conductor of electricity, whenconfigured as described herein, provides for this capability.

Referring to FIGS. 1 and 2, the conductor bar 12 preferably consistsessentially of a material having good electrical conductivity, such ascopper. Moreover, the conductor bar preferably has a first aspect, suchas defined by sides 14, which is dimensionally greater than a secondaspect, such as defined by a front 16, for consuming a minimum of spacein the direction of the second aspect. Which aspect is selected to bethe smaller aspect depends, for example, on the manner in which multiplecarrying devices are stacked or chained in the solution tank 13.Alternatively, the conductor bar 12 may simply have its first and secondaspects of similar dimension, such as, for example, where the conductorbar 12 has a square cross-section.

For the plating and etching of printed circuit board panels, it ispreferable that a carrying device 10 is disposed between and hasattached thereto edges of two articles held substantially in the sameplane, so that the sides 14 are disposed opposite one another, and sothat there are "N+1" number of carrying devices for "N" number ofpanels. Accordingly, it is preferable that the aspect corresponding to afront 17 of the panel, e.g. front 16, is narrow in order to fit morepanels into the tank 13.

The conductor bar 12 includes a buss connector 18 at a top end 20thereof. The buss connector makes good electrical contact with theconductor bar 12, such as may be achieved by soldering or welding thebuss connector 18 thereto. The buss connector is preferably adapted forreleasable attachment to the buss-bar 11; however the buss connector maybe adapted for attachment to other sources of electrical current. In apreferred form, the buss connector 18 is substantially of an inverted"J" shape, for hooking onto the buss-bar to allow the carrying device 10to be hung in the solution bath disposed there beneath. The shape andsize of the buss connector 18 should be such as to make a goodelectrical connection with the buss-bar 11. Solution in the bath doesnot, generally, reach the buss connector 18 or the connection thereof toconductor bar 12 when the carrying device 10 is partially immersed inthe bath; accordingly, the buss connector and its connection to theconductor bar need not be particularly corrosion resistant. The bussconnector 18 preferably consists essentially of a material having a goodelectrical conductivity, such as copper, and the connection to theconductor bar is, preferably, made by silver soldering the bussconnector 18 to the conductor bar 12 at 23.

The buss connector 18 includes a threaded aperture 24 for releasablyconnecting the buss connector to the buss-bar 11 by means of a threadedfastener 25, such as a "T" handle bolt. The threaded fastener providesfor a secure attachment of the conductor bar 12 to the buss-bar 11 aswell as a good electrical connection.

Referring to FIGS. 3A and 3B, the conductor bar 12 includes a cladding26 consisting essentially of a relatively high strength, metallic,corrosion resistant material, such as type 316 stainless steel orbetter. It is important that the cladding 26 make good electricalcontact with the conductor bar 12 along substantially the entire of thecladding-conductor bar interface, and that the cladding provide aliquid-tight seal. A preferred method for meeting these requirementsbreaks the cladding 26 into two elongate sections, such as symmetrical"L" shaped elongate sections 28, and a bottom cap 32. The sections arearranged, around the conductor bar 12, to conform to the external shapethereof Moreover, when the elongate sections are so arranged, theypreferably include lips 30. The lips 30 are utilized to provide materialfor welding, such as by inert-gas, the two elongate sections 28 to oneanother, thereby sealing the conductor bar 12. Moreover, when asubstantially pure copper conductor bar 12 is sealed with type 316stainless-steel cladding by welding, as is preferred, the two materialsexpand differently with the heat of the welding so that, upon cooling,the cladding is shrunk around the conductor bar 12,providing, by acompressive force exerted by the cladding 26 against the conductor bar12, good electrical contact that is reliable over the service life ofthe carrying device 10, for improving the delivery of current within thecarrying device 10. The bottom cap 32 is joined, as by welding, to theelongate sections 28 at a bottom end 34 of the conductor bar 12.Moreover, edges 36 of the elongate sections 28, are joined, as bywelding, to the conductor bar 12 at the top end 20 thereof, to create agas-tight seal at 36. While a preferred means for providing acompressive force by the cladding 26 has been described, other means,such as by driving or pressing the conductor 12 into an undersized tubeof the cladding 26, may be utilized without departing from the principleof the present invention.

The cladding 26 preferably includes a vent hole 38 which provides forthe escape of gases during the welding and concomitant heating. The venthole is welded or otherwise permanently sealed during the welding whilethe carrying device 10 is hot so that, upon cooling, a partial vacuum iscreated inside the cladding 26 by contraction of the remaining gases,further improving the electrical contact. It may now be appreciatedthat, although the carrying device 10 will generally not be immersed insolution up to the edges 36, and therefore the joining thereof to theconductor bar 12 need not resist the etchant, the seal 36 must begas-tight to maintain the partial vacuum.

Referring to FIG. 4, the cladding 26 includes a plurality of clampingmembers, such as anchors 40. The anchors 40 carry current from theconductor bar 12 through the cladding 26, to the article to be plated.Accordingly, the anchors 40 must make good electrical contact with thecladding 26 to which they are attached, must be good conductors ofelectricity, and must, along with the means by which they are joined tothe cladding, be resistant to corrosion. Preferably, the anchors 40consist essentially of the same material as does the cladding 26 and arejoined thereto by welding.

The anchors 40 include an anvil 42 and a fastening member 44, thefastening member including a fastening aperture 46, preferably athreaded hole for receiving a threaded fastener, such as a "T" handledbolt 48. The bolt 48, when threaded into the aperture 46 of thefastening member, may abut and be tightened against a face 47 of theanvil 42. The anchors 40 include an aperture, such as slot 50, disposedbetween the anvil 42 and the fastening member 44, the aperture beingadapted for receiving a portion of the article 15 to be plated, thearticle being pressed between the anvil face 47 and the bolt 48. Theslot 50 is more particularly adapted to receive an edge 51 of a printedcircuit board panel, as shown in FIG. 1; however, other aperture sizesand shapes may be utilized for receiving other articles, as will bereadily apparent to one of ordinary skill in the art.

The anvil 42 preferably includes a canal 52 for allowing solution,particularly plating solution, to flow underneath and contact thearticle 15. The canal 52, thence, provides for some plating of thearticle in an area otherwise covered by the anvil face 47, for example,to provide for a conductive path through that area. The use of canal 52is more advantageous to the extent the anvil is larger and thereforecovers more area of the article 15.

Referring back to FIG. 1, the anchors 40 are evenly spaced along sides14 to provide a relatively even current distribution. There are,preferably, six anchors to a side. Moreover, the anchors 40 on one ofthe sides 14 are staggered with respect to the anchors on the otherside, also for a more even distribution of current through the carryingdevice 10. Fewer anchors or more anchors may be utilized, however,without departing from the principles of the invention.

Referring to FIGS. 5A, 5B and 5C, each anchor 40 has a conductor pin 56associated therewith, for improving further the capability of thecarrying device 10 to deliver a large electrical current to the article15. The conductor bar 12 includes, in the vicinity of each anchor 40, apin aperture 54, the pin aperture preferably extending through theconductor bar, as shown in FIG. 5B; however, it may extend onlypartially thereinto, as shown in FIG. 5A. The pin aperture 54 is shapedto receive a pin 56 and is undersized, with respect to the pin, to betight-fitting with respect to the pin, so that a relatively large forceis required for insertion of the pin into the aperture. Preferably, theaperture 54 is a hole of 0.355 diameter, and pin 56 has a 0.375 majordiameter and tapers inwardly at a rate of 0.010 inches/inch. Moreover,the pin 56 is preferably about 2 inches long, so that its minor diameteris 0.355. The pin 56 is then inserted into the aperture 54 under a forceof about 2700 pounds. Any portion of the pin 56 left protruding beyondthe surface of the cladding 26 is then cut-off. This is advantageouslydone after the cladding 26 has been installed. The cladding 26 alsoincludes a corresponding pin aperture 58, on only one side 14 of thecladding if the pin extends only partially into the conductor bar 12, oron both sides of the cladding if the pin extends therethrough.

The pin 56 is adapted, preferably by being cut as described above, to besubstantially flush with a surface 57 of the cladding 26 when fullyseated into the aperture 54 and is button welded to the surface 57 at 59to seal the aperture 58, and to provide good electrical contact of thepin 56 to the cladding 26 in the vicinity of the anchors 40. The forceof insertion of the pin into the conductor bar 12 is partiallyresponsible for ensuring good and durable electrical contact therewith.Being proximate to the anchors 40, the pins 56 improve the delivery ofelectric current thereto.

Referring to FIGS. 5B and 6, the carrying device 10 is conformallycoated with a plastic material 61, such as by being dipped in plastisol,which is allowed to coat the entire device below the line of immersionin the tank 15, except at apertures 60. Apertures 60 allow for anopening to the cladding at the face 47 of the anvil 42, the aperturebeing flush thereto for providing electrical contact of the article 15with the face 47 when tightened against the anvil with the bolt 48.Apertures 60 further allow for an opening at an interior surface 47 ofthe fastening aperture 46, for allowing the bolt 48 to contact threadstherein. Moreover, the bolt 48 is preferably partially coated with aplastic material at portions 49 thereof that will be exposed to bathsolution when the bolt is fastened against the article to be plated.

Referring to FIGS. 7A and 7B, both showing the cladding 26 cut-away forclarity, the top end 20 of the conductor bar 12 preferably includesspaced-apart parallel grooves 64, around the circumference thereof. Thecladding 26 lying atop these grooves is depressed into those grooves, at66, the effect of the grooves and the depressions in the cladding beingto allow for some thermally induced displacement of the cladding 26 withrespect to the conductor bar 12 in an area where such minimaldisplacement is not so critical.

Referring back to FIGS. 1, 2 and 4, the carrying device 10 is preferablyutilized by hooking the buss connector 18 over the buss-bar 22 and, atthe threaded aperture 24, bolting the connector thereto by means of athreaded fastener, such as a "T" handle bolt. Preferably, a plurality ofcarrying devices 10 are so attached to the bus-bar, for carrying aplurality of printed circuit board panels 15. Edges 51 of the panels 15are inserted into the slots 50 of the anchors, an edge 51 of one panelbeing fitted into the slots of all the anchors on one side of thecarrying device, and an edge 51 of another panel being fitted into theslots of all the anchors on an opposite side of the carrying device.Thence, two carrying devices 10 contribute to the carrying of one panel,while, with the exception of the carrying devices 10 at both ends of atrain of panels, one carrying device 10 contributes to the carrying oftwo panels. The panels are fastened into the carrying device at theanchors by tightening a threaded fastener 48, carried by the fasteningmember 44 through the fastening aperture 46, against the anvil 42. Lowerportions of the carrying devices 10 and the entire portion of the panels15 desired to be electroplated or etched are subsequently immersed in aselected solution. When it is desired to electroplate, the solutionconsists essentially of a metallic salt and the buss-bar is energized toprovide large currents at low voltages, typically about 75 amps at 2volts through each carrying device 10. Means of completing the circuitwithin the solution are thence also provided as is well known in theart. When it is desired to etch, the buss-bar 11 is not energized andthe solution consists essentially of an acid, such as nitric orhydrofluoric acid.

A specific carrying device 10 adapted for electroplating of a particulararticle 15 and a method for improving the delivery of current thereinaccording to the present invention has been described above aspreferred, however, it will be apparent to one of ordinary skill in theart that other configurations may be advantageous when plating oretching other articles.

Moreover, the terms and expressions which have been employed in theforegoing specification are used therein as terms of description and notof limitation, and there is no intention of the use of such terms andexpressions of excluding equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

I claim:
 1. A device for carrying an article to be electroplated,comprising:a conductor, mechanically and electrically attachable to asource of electric current; a corrosion resistant, electricallyconductive cladding disposed around said conductor for sealing andmaking electrical contact with said conductor, said conductor and saidcladding each having a corresponding respective aperture therein; and anelectrically conductive pin disposed in said apertures in said claddingand said conductor, said pin disposed in said aperture of said conductorunder compressive stress, said pin contacting said conductor and saidcladding to provide electrical continuity therebetween, wherein saidcompressive stress being employed to increase the electrical continuitytherebetween.
 2. The carrying device of claim 1, wherein the electricalconductivity of said conductor is greater than the electricalconductivity of said cladding.
 3. The carrying device of claim 1,wherein said cladding exerts a compressive force against said conductor.4. The carrying device of claim 3, wherein said cladding comprises twosymmetrical sections wherein, the symmetrical sections are joined so asto shrink fit around said conductor.
 5. The carrying device of claim 1,further comprising an electrically conductive clamping member, saidclamping member depending from said cladding for holding and providingelectrical current to the article.
 6. The carrying device of claim 5,wherein said pin is disposed proximate said clamping member forimproving the electrical conductivity of said clamping member.
 7. Thecarrying device of claim 1, further including a vent aperture in saidcladding for releasing of gases, wherein said vent aperture is optinallysealed after the release of the gases.
 8. A device for carring anarticle to be electroplated, comprising:a conductor, mechanically andelectrically attachable to a source of electric current; a corrosionresistant, electrically conductive cladding disposed around saidconductor for sealing and making electrical contact with said conductor,said conductor and said cladding each having a corresponding respectiveaperture therein; an electrically conductive pin disposed in saidapertures in said cladding and said conductor, said pin disposed in saidaperture of said conductor under compressive stress, said pin contactingsaid conductor and said cladding to provide electrical continuitytherebetween; and a substantially conformal plastic coating.
 9. A devicefor carrying an article to be electroplated, comprising:a conductor,mechanically and electrically attachable to a source of electriccurrent; a corrosion resistant, electrically conductive cladding,disposed around said conductor for sealing and making electrical contactwith said conductor, said conductor and said cladding each having acorresponding respective aperture therein; an electrically conductivepin disposed in said apertures in said cladding and said conductor, saidpin disposed in said aperture of said conductor under compressivestress, said pin contacting said conductor and said cladding to provideelectrical continuity therebetween; and an electrically conductiveclamping member, said clamping member depending from said cladding forholding and providing electrical current to the article, wherein saidclamping member includes an anvil and a threaded fastener adapted fortightening the article against said anvil.
 10. The carrying device ofclaim 9, further comprising a substantially conformal plastic coating,said coating having an aperture disposed at a face of said anvil,wherein said aperture is flushed with said face providing for electricalcontact of the article with said face when tightened.
 11. A device forcarrying an article to be electroplated, comprising:a conductor,mechanically and electrically attachable to a source of electriccurrent; a corrosion resistant, electrically conductive claddingdisposed around said conductor for sealing and making electrical contactwith said conductor, said conductor and said cladding each having acorresponding respective aperture therein; an electrically conductivepin disposed in said apertures in said cladding and said conductor, saidpin disposed in said aperture of said conductor under compressivestress, said pin contacting said conductor and said cladding to provideelectrical continuity therebetween; and a plurality of spaced-apart,substantially parallel grooves in said conductor, wherein said claddingincludes a plurality of depressions corresponding to and depressed intosaid grooves, for absorbing thermal displacement of said cladding withrespect to said conductor.
 12. A device for carrying an article to beelectroplated, comprising:a conductor, mechanically and electricallyattachable to a source of electric current; a corrosion resistant,electrically conductive cladding disposed around said conductor forsealing and making electrical contact with said conductor, saidconductor and said cladding each having a corresponding respectiveaperture therein; an electrically conductive pin disposed in saidapertures in said cladding and said conductor, said pin disposed in saidaperture of said conductor under compressive stress, said pin contactingsaid conductor and said cladding to provide electrical continuitytherebetween, wherein said conductor is elongate, the device includinganchors depending from said cladding for holding and providingelectrical current to the article, said anchors having an anvil and athreaded fastener adapted for tightening the article against said anvil,six equally spaced first anchors disposed on one side of said conductor,and six equally spaced, corresponding, second anchors disposed on anopposite side of said conductor.
 13. A device for carrying an article tobe electroplated, comprising:a conductor, mechanically and electricallyattachable to a source of electric current; a corrosion resistant,electrically conductive cladding disposed around said conductor forsealing and making electrical contact with said conductor, and aplurality of spaced-apart, substantially grooves in said conductor,wherein said cladding includes a plurality of depressions correspondingto and depressed into said grooves, for absorbing thermal displacementof said cladding with respect to said conductor.
 14. A device forcarrying an article to be electroplated, comprising:a conductor,mechanically and electrically attachable to a source of electriccurrent; a corrosion resistant, electrically conductive claddingdisposed around said conductor for sealing and making electrical contactwith said conductor, wherein the electrical conductivity of saidconductor is substantially greater than the electrical conductivity ofsaid cladding, wherein the coefficient of expansion of said conductor isless than the coefficient of expansion of said cladding, and whereinsaid cladding exerts a compressive force on said conductor, to increasethe electrical continuity between said cladding and said conductor, saidcladding having two sections which are disposed adjacent respectiveperipheral surface portions of said conductor, abut one another and arewelded together so that, after welding, they exert said compressiveforce on said conductor.